Rapid prediction method for steady-state working frequency of LCC converter

Abstract

The invention relates to the technical field of DC / DC resonant converters, in particular to a rapid prediction method for the steady-state working frequency of an LCC converter, and the method comprises the steps: collecting the parameters of the LCC converter in real time; establishing a steady-state working frequency prediction model; determining a load range based on the collected parameters; determining a maximum frequency initial value and a minimum frequency initial value of the LCC converter based on the load range; and based on the maximum frequency initial value, the minimum frequency initial value and the steady-state working frequency prediction model, determining an approximate value of the steady-state working frequency of the LCC converter through a segmented linear approximation method and a two-point method. Through the prediction method, when the circuit state or the circuit parameters change, the steady-state working frequency approximate value of the LCC converter can be rapidly predicted, so that the state trajectory model based on the steady-state working frequency approximate value is more accurate.

Description

Technical Field

[0001] The invention relates to the technical field of DC / DC resonant converters, and in particular to a method for quickly predicting the steady-state operating frequency of an LCC converter. Background Art

[0002] In order to achieve the optimal dynamic response, it is difficult for the existing technology to obtain the steady-state operating state and the corresponding operating frequency of any target point according to the load conditions in a short time, which severely limits the application of the state trajectory. If the main controller can obtain the steady-state operating frequency of the LCC converter in the new state within one or several cycles after the load mutation, the dynamic response speed of the converter can be greatly improved. Various nonlinear control and advanced control algorithms can also be further applied to the LCC converter. The precise time model of the LCC converter that has been established is too complex due to the three resonant elements in the LCC converter and the nonlinear characteristics of the LCC converter, and the general controller cannot solve it in a short time.

[0003] In the prior art, a method for calculating the root mean square value of the resonant current of the corresponding LCC converter in the steady state according to the load current is also proposed. On this basis, the new target state can be obtained in one cycle. However, this method is only applicable to LLC converters operating at the resonant frequency point. Another work gives an average model to describe the state of the LCC converter. This method has a simple model and can be solved by a general controller. But it is only applicable to LCC converters operating at the resonant frequency point. There are several problems with the above method. On the one hand, due to the nonlinear gain characteristics of the LCC converter itself, if you want to accurately describe the characteristics of the converter by looking up the table, you need to store a large amount of data, which will greatly occupy the resources of the controller; on the other hand, when the circuit parameters change, it is necessary to simulate again on a large scale to establish a new table, which has poor flexibility and poor model adaptability. Finally, because it is not a prediction method based on model establishment, it cannot be combined with advanced algorithms such as machine learning and predictive control.

[0004] For example, in the prior art, a Chinese invention patent document with publication number CN113346728A and publication date September 3, 2021, only uses the theoretical steady-state operating frequency when confirming the state trajectory. When the circuit state or circuit parameters (including load) change, the steady-state operating frequency will change. Only using the theoretical steady-state operating frequency will make the obtained state trajectory model inaccurate. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a method for quickly predicting the steady-state operating frequency of an LCC converter. When the circuit state or circuit parameters (including load) changes, the approximate value of the steady-state operating frequency of the LCC converter can be quickly predicted, so that the state trajectory model based on the approximate value of the steady-state operating frequency is more accurate.

[0006] The present invention is achieved by adopting the following technical solutions:

[0007] A method for quickly predicting the steady-state operating frequency of an LCC converter comprises the following steps:

[0008] Step S1. Real-time acquisition of LCC converter parameters;

[0009] Step S2. Establishing a steady-state operating frequency prediction model;

[0010] Step S3. Determine the load range based on the parameters collected in step S1;

[0011] Step S4. Based on the load range, determine the maximum frequency initial value and the minimum frequency initial value of the LCC converter;

[0012] Step S5. Based on the maximum frequency initial value, the minimum frequency initial value and the steady-state operating frequency prediction model, the approximate value of the steady-state operating frequency of the LCC converter is determined by a piecewise linear approximation method and a two-point method.

[0013] The parameters include the LCC converter input voltage V in , LCC converter output voltage V o 、LCC converter series inductor L r 、LCC converter series capacitor C r 、LCC converter parallel capacitor C p , LCC converter output current I o And the transformer ratio n of the LCC converter.

[0014] The steady-state operating frequency prediction model in step S2 is an approximately linearized f(f sw )function:

[0015]

[0016] In the formula, is the time in the first mode, is the time in the second mode, is the time of the third mode, f sw is the steady-state operating frequency; the first mode refers to the resonant stage when the diode is closed and the LCC converter is connected in series with the inductor L r 、LCC converter series capacitor C rAnd the LCC converter parallel capacitor C p The second mode refers to the mode in which diodes D1 and D4 remain on during the resonance phase, and the LCC converter is connected in series with the inductor L r The capacitor C is connected in series with the LCC converter r The third mode refers to the mode in which diodes D2 and D3 are always turned on during the resonance phase, and the LCC converter is connected in series with the inductor L k The capacitor C is connected in series with the LCC converter r Modes participating in resonance.

[0017] The method for determining the approximate value of the steady-state operating frequency of the LCC converter in step S5 is:

[0018]

[0019] In the formula, F swtarget is the approximate value of the steady-state operating frequency of the LCC converter, f sw1 is the minimum frequency initial value, f(F sw1 ) is the minimum steady-state operating frequency, F(F sw0 ) is the maximum steady-state operating frequency, F sw0 is the initial value of the maximum frequency.

[0020] Step S5 specifically includes the following steps:

[0021] Step S 51 . Set the maximum frequency initial value f sw0 and the minimum frequency initial value f sw1 Input the steady-state operating frequency prediction model to obtain the maximum steady-state operating frequency f(f sw0 ) and the minimum steady-state operating frequency f(f sw1 );

[0022] Step S 52 . Obtain the steady-state operating frequency prediction model f(f sw ) is an approximate linear function f1(f sw ):

[0023]

[0024] Step S 53 .When the approximate linear function f1(f sw ) is equal to zero, solve the approximate value of the steady-state operating frequency f of the LCC converter swtarget :

[0025]

[0026] The time under the first mode is calculated as:

[0027]

[0028] Where V CpNt2 is the LCC converter parallel capacitor C p The voltage at time t2, V CpNt1 is the LCC converter parallel capacitor C p The voltage at time t1; time t1 represents the series inductance L of the LCC converter r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p Participate in resonance, time t2 represents the LCC converter series inductor L r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p Resonant steady state.

[0029] The calculation method for the time in the second mode is:

[0030]

[0031] Where V CpNt2 is the LCC converter parallel capacitor C p The voltage at time t2, V Cp2t3 is the LCC converter parallel capacitor C p The voltage at time t3, V CpNt4 is the LCC converter parallel capacitor C p The voltage at time t4; γ is The radius value under the mode; time t2 represents the series inductance L of the LCC converter r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p Resonant steady state, time t3 represents the LCC converter series inductor L r The capacitor C is connected in series with the LCC converter r Participate in resonance.

[0032] The calculation method of the time under the third mode is:

[0033]

[0034] Where V CpNt3 is the LCC converter parallel capacitor C p The voltage at time t3, V CpNt4 is the LCC converter parallel capacitor C p The voltage at time t4; time t3 represents the series inductance L of the LCC converter r The capacitor C is connected in series with the LCC converter rParticipate in resonance, time t4 represents the LCC converter series inductor L r The capacitor C is connected in series with the LCC converter r Resonant steady state.

[0035] LCC converter parallel capacitor C p The voltages at t1, t2, t3 and t4 are:

[0036]

[0037] Where V CpNt1 is the LCC converter parallel capacitor C p The voltage at time t1, V CpNt2 is the LCC converter parallel capacitor C p The voltage at time t2, V CpNt3 is the LCC converter parallel capacitor C p The voltage at time t3, V CpNt4 is the LCC converter parallel capacitor C p The voltage at time t4; time t1 represents the series inductance L of the LCC converter r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p Participate in resonance, time t2 represents the LCC converter series inductor L r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p Resonant steady state; time t3 represents the LCC converter series inductor L r The capacitor C is connected in series with the LCC converter r Participate in resonance, time t4 represents the LCC converter series inductor L r The capacitor C is connected in series with the LCC converter r Resonant steady state; V o is the output voltage of the LCC converter, n is the transformer ratio of the LCC converter, I o is the LCC converter output current, V in is the LCC converter input voltage, f sw is the steady-state operating frequency.

[0038] The load range includes light load, medium load and heavy load.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] 1. In the present invention, the piecewise linear approximation method can improve the accuracy of the predicted steady-state operating frequency approximation value. Combined with the two-point fast method, the solution speed is faster than the existing general controller solution method; more importantly, the circuit parameters are small. Compared with the exact solution, the error of the fast two-point method proposed by the present invention is less than 0.1%.

[0041] When the circuit parameters change, the fast two-point method has high adaptability. According to the tested electrical parameters of the LCC converter, it can guide the solution of the numerical solution steady-state frequency of the LCC converter, thereby realizing the state trajectory control of the LCC converter.

[0042] 2. This prediction method has a wider application range, and can be applied not only to LCC converters operating at resonant frequency points, but also to LCC converters operating at non-resonant frequency points. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, wherein:

[0044] Figure 1 It is a schematic diagram of the process of the present invention;

[0045] Figure 2 A schematic diagram of the effect of the fast two-point method of the LCC converter in the present invention;

[0046] Figure 3 is the resonant topological mode in the present invention Circuit diagram;

[0047] Figure 4 is the resonant topological mode in the present invention Circuit diagram;

[0048] Figure 5 is the resonant topological mode in the present invention Circuit diagram. DETAILED DESCRIPTION

[0049] Example 1

[0050] As a basic implementation mode of the present invention, the present invention includes a method for quickly predicting the steady-state operating frequency of an LCC converter, comprising the following steps:

[0051] Step S1. Collect the parameters of the LCC converter in real time.

[0052] Step S2: Establish a steady-state operating frequency prediction model.

[0053] Step S3: Determine the load range based on the parameters collected in step S1.

[0054] Step S4: Based on the load range, determine the maximum frequency initial value and the minimum frequency initial value of the LCC converter.

[0055] Step S5. Based on the maximum frequency initial value, the minimum frequency initial value and the steady-state operating frequency prediction model, the approximate value of the steady-state operating frequency of the LCC converter is determined by a piecewise linear approximation method and a two-point method.

[0056] Example 2

[0057] As a preferred embodiment of the present invention, the present invention includes a method for quickly predicting the steady-state operating frequency of an LCC converter, comprising the following steps:

[0058] Step S1. Real-time acquisition of LCC converter parameters. The parameters include LCC converter input voltage V in , LCC converter output voltage V o 、LCC converter series inductor L r 、LCC converter series capacitor C r 、LCC converter parallel capacitor C p , LCC converter output current I o And the transformer ratio n of the LCC converter.

[0059] Step S2. Establish a steady-state operating frequency prediction model. The steady-state operating frequency prediction model is an approximately linearized f(f sw )function:

[0060]

[0061] In the formula, is the time in the first mode, is the time in the second mode, is the time of the third mode, f sw is the steady-state operating frequency; the first mode refers to the resonant stage when the diode is closed and the LCC converter is connected in series with the inductor L r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p The second mode refers to the mode in which diodes D1 and D4 remain on during the resonance phase, and the LCC converter is connected in series with the inductor L r The capacitor C is connected in series with the LCC converter r The third mode refers to the mode in which diodes D2 and D3 are always turned on during the resonance phase, and the LCC converter is connected in series with the inductor L r The capacitor C is connected in series with the LCC converter r Modes participating in resonance.

[0062] Step S3: Determine the load range based on the parameters collected in step S1, wherein the load range includes light load, medium load and heavy load.

[0063] Step S4: Based on the load range, determine the maximum frequency initial value and the minimum frequency initial value of the LCC converter.

[0064] Step S5. Based on the maximum frequency initial value, the minimum frequency initial value and the steady-state operating frequency prediction model, the approximate value of the steady-state operating frequency of the LCC converter is determined by a piecewise linear approximation method and a two-point method.

[0065] Example 3

[0066] As another preferred embodiment of the present invention, the present invention includes a method for quickly predicting the steady-state operating frequency of an LCC converter, comprising the following steps:

[0067] Step S1. Collect the parameters of the LCC converter in real time.

[0068] Step S2. Establish a steady-state operating frequency prediction model. The steady-state operating frequency prediction model is an approximately linearized f(f sw )function:

[0069]

[0070] In the formula, is the time in the first mode, is the time in the second mode, is the time of the third mode, f sw is the steady-state operating frequency; the first mode refers to the resonant stage when the diode is closed and the LCC converter is connected in series with the inductor L r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p The second mode refers to the mode in which diodes D1 and D4 remain on during the resonance phase, and the LCC converter is connected in series with the inductor L r The capacitor C is connected in series with the LCC converter r The third mode refers to the mode in which diodes D2 and D3 are always turned on during the resonance phase, and the LCC converter is connected in series with the inductor L r The capacitor C is connected in series with the LCC converter r Modes participating in resonance.

[0071] Step S3: Determine the load range based on the parameters collected in step S1.

[0072] Step S4: Based on the load range, determine the maximum frequency initial value and the minimum frequency initial value of the LCC converter.

[0073] Step S5. Based on the maximum frequency initial value, the minimum frequency initial value and the steady-state operating frequency prediction model, the approximate value of the steady-state operating frequency of the LCC converter is determined by the piecewise linear approximation method and the two-point method:

[0074]

[0075] In the formula, f swtarget is the approximate value of the steady-state operating frequency of the LCC converter, f sw1 is the minimum frequency initial value, f(f sw1 ) is the minimum steady-state operating frequency, f(f sw0 ) is the maximum steady-state operating frequency, f sw0 is the initial value of the maximum frequency.

[0076] Example 4

[0077] As another preferred embodiment of the present invention, the present invention includes a method for quickly predicting the steady-state operating frequency of an LCC converter. Figure 1 , including the following steps:

[0078] Step S1. Real-time acquisition of LCC converter parameters. The parameters include LCC converter input voltage V in , LCC converter output voltage V o 、LCC converter series inductor L r 、LCC converter series capacitor C r 、LCC converter parallel capacitor C p , LCC converter output current I o And the transformer ratio n of the LCC converter.

[0079] Step S2: Establish a steady-state operating frequency prediction model.

[0080] For details, please refer to the attached manual. Figure 3 ~Instructions attached Figure 5 The parallel capacitance C of the LCC converter can be solved by the following formula: p The voltage at t1, t2, t3 and t4:

[0081]

[0082] Where V CpNt1 is the LCC converter parallel capacitor C p The voltage at time t1, V CpNt2 is the LCC converter parallel capacitor C p The voltage at time t2, V CpNt3 is the LCC converter parallel capacitor C o The voltage at time t3, V CpNt4is the LCC converter parallel capacitor C p The voltage at time t4. Time t1 represents the series inductance L of the LCC converter. r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p Participate in resonance; time t2 represents the LCC converter series inductor L r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p Resonant steady state; time t3 represents the LCC converter series inductor L r The capacitor C is connected in series with the LCC converter r Participate in resonance; time t4 represents the LCC converter series inductor L r The capacitor C is connected in series with the LCC converter r Resonant steady state.

[0083] According to the above LCC converter parallel capacitor C p The voltage values ​​at t1, t2, t3 and t4 can be obtained and Time in three modes:

[0084]

[0085] Where γ is The radius value under the mode is expressed as follows:

[0086]

[0087] In the formula, is the time in the first mode, is the time in the second mode, is the time of the third mode, f sw The first mode refers to the resonant stage when the diode is turned off and the LCC converter is connected in series with the inductor L r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p The second mode refers to the mode in which diodes D1 and D4 remain on during the resonance phase, and the LCC converter is connected in series with the inductor L r The capacitor C is connected in series with the LCC converter r The third mode refers to the mode in which diodes D2 and D3 are always turned on during the resonance phase, and the LCC converter is connected in series with the inductor L r The capacitor C is connected in series with the LCC converter r Modes participating in resonance.

[0088] Above and The sum of the times is the resonant half period, and the resonant switching frequency can be further solved. The steady-state equation is as follows:

[0089]

[0090] The steady-state operating frequency prediction model is established as an approximately linearized f(f sw )function:

[0091]

[0092] Step S3: Determine the load range based on the parameters collected in step S1. Specifically, the load range can be determined based on the output voltage V o And the LCC converter output current I o Determine a load range, which includes light load, medium load and heavy load. For example, when the output current of the LCC converter is 0.85A-1.4A, it is a light load; when the output current of the LCC converter is 1.4A-2A, it is a medium load; when the output current of the LCC converter is 2A-3.2A, it is a heavy load.

[0093] Step S4. Determine the initial value f of the maximum frequency of the LCC converter based on the load range sw0 and the minimum frequency initial value f sw1 .

[0094] Step S5. Based on the maximum frequency initial value, the minimum frequency initial value and the steady-state operating frequency prediction model, the approximate value of the steady-state operating frequency of the LCC converter is determined by the piecewise linear approximation method and the two-point method. Specifically, the following steps are included:

[0095] Step S 51 . A fast two-point method is proposed, where the maximum frequency initial value f sw0 and the minimum frequency initial value f sw1 Input the steady-state operating frequency prediction model to obtain the maximum steady-state operating frequency f(f sw0 ) and the minimum steady-state operating frequency f(f sw1 ).

[0096] Step S 52 On this basis, the steady-state operating frequency prediction model f(f sw ) of the approximate linear function f1(f sw ):

[0097]

[0098] Step S 53 .When the approximate linear function f1(f sw) is equal to zero, solve the approximate value of the steady-state operating frequency f of the LCC converter swtarget :

[0099]

[0100] At the same time, in this method, the approximate linear function is given by the maximum frequency initial value f sw0 and the minimum frequency initial value f sw1 If the maximum frequency initial value f sw0 and the minimum frequency initial value f sw1 The closer to the exact value, the better the linear function can describe the function f(f sw ), which means that the error of the approximate solution will be smaller. After the LCC converter is designed and implemented, the switching frequency range is determined.

[0101] To better illustrate the prediction method, an LCC resonant converter with the following parameters is used as an example: input voltage is 90V, output voltage is 64A, output current is 0.85-3.2A, transformer ratio is 5:4, series resonant inductor is 70uH, series resonant capacitor is 52.8nF, parallel resonant capacitor is 22.7nF, and digital controller model is TMS320F28377D. The frequency range of current from 0.85A to 1.4A is 185kHz to 160kHz. The frequency range of current from 1.4A to 2.0A is 160kHz to 140kHz. The frequency range of current from 2.0A to 3.2A is 140kHz to 120kHz.

[0102] The accuracy of the above solution is improved by using the piecewise linear approximation method. The load range of the LCC converter can be divided into light load, medium load and heavy load. Therefore, the frequency range under different load ranges is determined. According to the characteristics of the LCC converter, the heavier the load, the lower the operating frequency. The maximum and minimum values ​​of the corresponding frequency range under different load ranges are selected as the initial value f sw0 and f sw1 The effect of the two-point quick method is shown in the instructions. Figure 2 , in the figure, f swaccurare is the precise value of the LCC converter frequency. Compared with the exact solution, the error of the fast two-point method proposed by the present invention is less than 0.1%.

[0103] When I o When the frequency is known, the initial value of the frequency can be determined according to the above range. Then, the above formula f swtarget Find the approximate steady-state operating frequency. For example, if I o is 1.0A, then the initial frequency value f sw0 and f sw1 are 185kHz and 160kHz respectively, so f swtargetis 176.83kHz. And it is through the function f(f sw )The exact solution obtained by computer is 176.96kHz.

[0104] After solving the approximate value of the steady-state operating frequency, substituting it into the following formula can obtain the state trajectory of the switching topology under steady-state conditions.

[0105]

[0106]

[0107] After a sudden load change occurs, the goal of the LCC converter is to control the state trajectory corresponding to the steady-state operating frequency approximately solved according to the target state trajectory, thereby realizing the state trajectory control of the LCC converter.

[0108] This prediction method can quickly solve the approximate numerical solution of the steady-state frequency. Compared with the existing general controller solution method, the solution speed is faster; more importantly, the circuit parameters are small. When the circuit parameters change, the fast two-point method has high adaptability. According to the tested LCC converter electrical parameters, it can guide the solution of the numerical solution steady-state frequency of the LCC converter. The fast two-point method has fast dynamic response and small error.

[0109] In summary, after reading the present invention document, ordinary technicians in this field can make various other corresponding transformation schemes based on the technical scheme and technical concept of the present invention without creative mental labor, which all fall within the scope of protection of the present invention.

Claims

1. A method for rapidly predicting the steady-state operating frequency of an LCC converter, characterized in that: The following steps are involved: Step S1. Real-time acquisition of LCC converter parameters; Step S2. Establishing a steady-state operating frequency prediction model; Step S3. Determine the load range based on the parameters collected in step S1; Step S4. Based on the load range, determine the maximum frequency initial value and the minimum frequency initial value of the LCC converter; Step S5. Based on the maximum frequency initial value, the minimum frequency initial value and the steady-state operating frequency prediction model, the approximate value of the steady-state operating frequency of the LCC converter is determined by a piecewise linear approximation method and a two-point method.

2. The method for rapidly predicting the steady-state operating frequency of an LCC converter according to claim 1, characterized in that: The parameters include the LCC converter input voltage V in , LCC converter output voltage V o 、LCC converter series inductor L r 、LCC converter series capacitor C r 、LCC converter parallel capacitor C p , LCC converter output current I o And the transformer ratio n of the LCC converter.

3. The method for rapidly predicting the steady-state operating frequency of an LCC converter according to claim 1, characterized in that: The steady-state operating frequency prediction model in step S2 is an approximately linearized f(f sw )function: In the formula, is the time in the first mode, is the time in the second mode, is the time of the third mode, f sw is the steady-state operating frequency; the first mode refers to the resonant stage when the diode is closed and the LCC converter is connected in series with the inductor L r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p The second mode refers to the mode in which diodes D1 and D4 remain on during the resonance phase, and the LCC converter is connected in series with the inductor L r The capacitor C is connected in series with the LCC converter r The third mode refers to the mode in which diodes D2 and D3 are always turned on during the resonance phase, and the LCC converter is connected in series with the inductor L r The capacitor C is connected in series with the LCC converter r Modes participating in resonance.

4. A method for rapidly predicting the steady-state operating frequency of an LCC converter according to claim 1 or 3, characterized in that: The method for determining the approximate value of the steady-state operating frequency of the LCC converter in step S5 is: In the formula, f swtarget is the approximate value of the steady-state operating frequency of the LCC converter, f sw1 is the minimum frequency initial value, f(f sw1 ) is the minimum steady-state operating frequency, f(f sw0 ) is the maximum steady-state operating frequency, f sw0 is the initial value of the maximum frequency.

5. The method for rapidly predicting the steady-state operating frequency of an LCC converter according to claim 4, characterized in that: Step S5 specifically includes the following steps: Step S 51 . Set the maximum frequency initial value f sw0 and the minimum frequency initial value f sw1 Input the steady-state operating frequency prediction model to obtain the maximum steady-state operating frequency f(f sw0 ) and the minimum steady-state operating frequency f(f sw1 ); Step S 52 . Obtain the steady-state operating frequency prediction model f(f sw ) is an approximate linear function f1(f sw ): Step S 53 .When the approximate linear function f1(f sw ) is equal to zero, solve the approximate value of the steady-state operating frequency f of the LCC converter swtarget :

6. The method for rapidly predicting the steady-state operating frequency of an LCC converter according to claim 3, characterized in that: The time under the first mode is calculated as: Where V CpNt2 is the LCC converter parallel capacitor C p The voltage at time t2, V CpNt1 is the LCC converter parallel capacitor C p The voltage at time t1; time t1 represents the series inductance L of the LCC converter r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p Participate in resonance, time t2 represents the LCC converter series inductor L r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p Resonant steady state.

7. The method for rapidly predicting the steady-state operating frequency of an LCC converter according to claim 3, characterized in that: The calculation method for the time in the second mode is: Where V CpNt2 is the LCC converter parallel capacitor C p The voltage at time t2, V CpNt3 is the LCC converter parallel capacitor C p The voltage at time t3, V CpNt4 is the LCC converter parallel capacitor C p The voltage at time t4; γ is The radius value under the mode; time t2 represents the series inductance L of the LCC converter r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p Resonant steady state, time t3 represents the LCC converter series inductor L r The capacitor C is connected in series with the LCC converter r Participate in resonance.

8. The method for rapidly predicting the steady-state operating frequency of an LCC converter according to claim 3, characterized in that: The calculation method of the time under the third mode is: Where V CpNt3 is the LCC converter parallel capacitor C p The voltage at time t3, V CpNt4 is the LCC converter parallel capacitor C p The voltage at time t4; time t3 represents the series inductance L of the LCC converter r The capacitor C is connected in series with the LCC converter r Participate in resonance, time t4 represents the LCC converter series inductor L r The capacitor C is connected in series with the LCC converter r Resonant steady state.

9. The method for rapidly predicting the steady-state operating frequency of an LCC converter according to claim 3, characterized in that: LCC converter parallel capacitor C p The voltages at t1, t2, t3 and t4 are: Where V CpNt1 is the LCC converter parallel capacitor C p The voltage at time t1, V CpNt2 is the LCC converter parallel capacitor C p The voltage at time t2, V CpNt3 is the LCC converter parallel capacitor C p The voltage at time t3, V CpNt4 is the LCC converter parallel capacitor C p The voltage at time t4; time t1 represents the series inductance L of the LCC converter r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p Participate in resonance, time t2 represents the LCC converter series inductor L r 、LCC converter series capacitor C r And the LCC converter parallel capacitor C p Resonant steady state; time t3 represents the LCC converter series inductor L r The capacitor C is connected in series with the LCC converter r Participate in resonance, time t4 represents the LCC converter series inductor L r The capacitor C is connected in series with the LCC converter r Resonant steady state; V o is the output voltage of the LCC converter, n is the transformer ratio of the LCC converter, I o is the LCC converter output current, V in is the LCC converter input voltage, f sw is the steady-state operating frequency.

10. The method for rapidly predicting the steady-state operating frequency of an LCC converter according to claim 1, characterized in that: The load range includes light load, medium load and heavy load.

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